VOLUNTARY ANNOUNCEMENT - NEW DRUG APPLICATION FOR KN026 (ANBENITAMAB INJECTION) ACCEPTED BY THE NMPA

Hong Kong Exchanges and Clearing Limited and The Stock Excha nge of Hong Kong Limited take no responsibility for the contents of this announcement, make no representation as to its accuracy or completeness and expressly disclaim any liability whatsoe ver for any loss howsoever arising from or in reliance upon the whole or any part of the contents of this ann ouncement. CSPC PHARMACEUTICAL GROUP LIMITED (Incorporated in Hong Kong with limited liability) (Stock Code: 1093) ʮ ̡ VOLUNTARY ANNOUNCEMENT NEW DRUG APPLICATION FOR KN026 (ANBENITAMAB INJECTION) ACCEPTED BY THE NMPA The Board of Directors (the ‘‘Board ’’) of CSPC Pharmaceutical Group Limited (the ‘‘Company ’’, together with its subsidiaries, the ‘‘Group ’’) is pleased to announce that the new drug application for KN026 (Anbenitamab Injection) (the ‘‘Product ’’) co-developed by CSPC Shanghai JMT-Bio Technology Co., Ltd., a subsidiary of the Company, and Jiang su Alphamab Oncology Co., Ltd. has been accepted by the National Medical Products Administrat ion (the ‘‘NMPA ’’) of the People ’s Republic of China. The Product has been applied for as a Class 1 therapeutic biol ogical product. Its indication is for use in combination with chemotherapy for the treatment of patient s with HER2-positive locally advanced, recurrent, or metastatic gastric or gastroesophageal junc tion cancer who have failed at least one prior systemic therapy (which must include trastuzumab in combin ation with chemotherapy). Previously, the Product was granted Breakthrough Therapy Designation on 4 N ovember 2023 and Priority Review on 28 August 2025 by the Center for Drug Evaluation of the NMPA. The Product is an anti-HER2 bispecific antibody that can sim ultaneously bind two non-overlapping epitopes of HER2, leading to HER2 signaling blockade. The re sults of a Phase II clinical trial of the Product were first presented at the European Society for Med ical Oncology (ESMO) Congress 2024. The study results demonstrated that the Product in combinat ion with chemotherapy achieved an objective response rate of 40.0%, with a median progression -free survival of 8.6 months and a median overall survival of 13.2 months as assessed by the Independe nt Review Committee (IRC). This new drug application is primarily based on a pivotal Phase II/II I clinical trial (KC-WISE). The first interim analysis results of the Phase III clinical study indicated t hat, compared to the current standard of care, the Product in combination with chemotherapy significantl y improved clinical efficacy by prolonging progression-free survival and overall survival, with no ne w safety signals, a low incidence of cardiotoxicity, and low immunogenicity in terms of safety p rofile. – 1 – Currently, there are no approved anti-HER2 drugs for the sec ond-line treatment of HER2-positive gastric cancer. The Product is the first anti-HER2 bispecif ic antibody drug in China to achieve positive results in the second-line treatment of gastric cancer. Bas ed on the first interim analysis results of the pivotal Phase II/III clinical study (KC-WISE) of the Produc t, the Group submitted the new drug application to the NMPA on 7 September 2025. Meanwhile, the G roup is also actively promoting multiple clinical trials of the Product for different indic ations of solid tumors, among which the development for indications of gastric cancer and breast ca ncer has entered the pivotal Phase III clinical trial stage, with the aim of benefiting more patien ts. By Order of the Board CSPC Pharmaceutical Group Limited CAI Dong Chen Chairman Hong Kong, 11 September 2025 As at the date of this announcement, the Board comprises Mr. C AI Dong Chen, Mr. ZHANG Cuilong, Mr. WANG Zhenguo, Mr. PAN Weidong, Mr. WANG Huaiyu, Dr. LI Chu nlei, Dr. YAO Bing, Mr. CAI Xin and Mr. CHEN Weiping as executive directors; and Mr. WANG Bo, Mr. CHEN Chuan, Prof. WANG Hongguang, Mr. AU Chun Kwok Alan, Mr. LAW Cheuk Kin Steph en and Ms. LI Quan as independent non-executive directors. – 2 –

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